The invention pertains to the field of input devices for handheld computers in general, and to PCMCIA defined PC Card interfaces between barcode scanning devices and other input devices and portable computers in particular.
Barcodes are patterns of light and dark spaces, usually arranged as a series of parallel bars of varying width and having variable width white spaces between the bars. The pattern of light and dark spaces and ratios of light to dark spaces over the length of the barcode encode therein a series of alphanumeric characters. Barcodes are widely used on products to encode the product description etc. in, for example, supermarkets and departments stores. Items to be purchased or inventoried have their barcodes scanned by laser or charge coupled device barcode scanning engines which are coupled to host computers. The pattern of light and dark spaces detected by the barcode scanning engine is converted to an electrical signal having a unique pattern dictated by the pattern of light and dark spaces. This electrical signal is decoded and converted to the alphanumeric string encoded in the barcode either by the host computer or by the barcode scanning engine. The alphanumeric string either directly or indirectly specifies the product description and price in most applications and may specify other information.
Portable barcode scanning systems are useful for many applications such as inventory control. Portable barcode scanning systems exist in the prior art and are commercially available from such vendors as Symbol Technologies, Inc. of Bohemia, New York and Telxon. To date however portable barcode scanners have been custom units of proprietary design. An example of a custom designed, proprietary portable barcode scanning system is the model PTC-600 available from Telxon. This device uses a custom designed portable computer to which is attached a clip-on barcode scanning engine. This technology is described in more detail in U.S. Pat. No. 4,621,189, the teachings of which are incorporated by reference. However the process of decoding barcodes is well known and can be done by any suitably programmed computer having appropriate interface circuitry so there is no need to buy a custom designed computer system simply to do one type of task when a general purpose computer with suitable peripheral circuitry and software can do the same task as well as other tasks. Further, there is a disadvantage to the consumer in that as better barcode scanning engines or better computers become available, the consumer is precluded from using them in a custom designed system unless he or she is willing to give up their investment in the custom designed system already purchased.
With the introduction of palmtop computers, Personal Communicators such as the AT&T EO and Personal Digital Assistants (hereafter PDA's) there has arisen a need to modify these general purpose devices for use with various input devices such as barcode scanning engines to create "open system" non-proprietary portable barcode scanning apparati.
Therefore, there is described herein an open system interface for various input devices such as bar code scanners, magnetic stripe readers etc. which can be integrated onto a PCMCIA defined PC Card.